The present invention relates to a process for the regeneration of a slurry used in rechargeable zinc-air batteries, generally, and more particularly, to such rechargeable electric batteries intended for use in electric vehicles and energy storage systems.
Various proposals have been made in the past for electric powered vehicles. To date, for a number of reasons, electric vehicle systems have yet to become commercially viable, generally, for urban and highway applications.
There have been proposals to employ zinc/air batteries for urban vehicle propulsion. An example is the following publication: Improved slurry zinc/air systems as batteries for urban vehicle propulsion, by P. C. Foller, Journal of Applied Electrochemistry 16 (1986), 527-543.
Metal/air battery structures are described in the following publications: U.S. Pat. No. 4,842,963, entitled Zinc Electrode and Rechargeable Zinc-Air Battery; U.S. Pat. No. 4,147,839, entitled Electrochemical Cell with Stirred Slurry; U.S. Pat. No. 4,908,291, entitled Metal/air Battery with Recirculating Electrolyte; U.S. Pat. No. 3,847,671, entitled Hydraulically-Refuelable Metal-Gas Depolarized Battery System; U.S. Pat. No. 4,925,744, entitled Primary Aluminum-Air Battery; U.S. Pat. No. 3,716,413, entitled Rechargeable Electrochemical Power Supply; U.S. Pat. No. 4,925,744, entitled Primary Aluminum-Air Battery. In U.S. Pat. No. 3,592,698, entitled Metal Fuel Battery with Fuel Suspended in Electrolyte, there is described inter alia a method for circulating an electrolyte/metal fuel powder mixture through the batteries; U.S. Pat. No. 4,126,733, entitled Electrochemical Generator Comprising an Electrode in the Form of a Suspension, relates to a similar subject using a circulated suspension of inert cores coated with an electrochemically active material. In U.S. Pat. No. 4,341,847, entitled "Electrochemical Zinc-Oxygen Cell", there is described a method in which an electrolyte is circulated in the annular space between concentric electrodes.
Electrical energy storage systems are described in the following publications: U.S. Pat. No. 4,843,251 entitled Energy Storage and Supply Recirculating Electrolyte; Energy on Call by John A. Casazza et al, IEEE Spectrum June, 1976, pp 44-77; U.S. Pat. No. 4,275,310, entitled Peak Power Generation; U.S. Pat. No. 4,124,805, entitled Pollution-Free Power Generating and Peak Power Load Shaving System; U.S. Pat. No. 4,797,566, entitled Energy Storing Apparatus.
Regeneration of spent zinc-containing alkaline electrolyte is described in a number of prior patents. For example, in U.S. Pat. No. 3,847,671 (mentioned above) whole spent electrolyte is subjected to electrolysis, when zinc deposited at the cathode is removed with a wiper blade. The thus-removed zinc is said to be substantially heavier than the electrolyte (35-40% KOH) and thus falls to the bottom of each cell. In a particular embodiment, the cathode and anode are specified as being made from copper (or silver-plate copper) and carbon, respectively. In U.S. Pat. No. 3,981,747, it is proposed to regenerate the spent zinc in an alkaline electrolyte by reaction with a strongly electronegative metal, such as magnesium or aluminum, which displaces the zinc. In U.S. Pat. No. 4,341,847 (also mentioned above), spent zinc in the alkaline electrolyte is regenerated either by reversing the current and plating zinc on the anode, or by merely mechanically replacing zinc oxide particles by active zinc particles.
The disclosures of all of the foregoing publications (including patents) are explicitly incorporated herein by reference.